On 12/25/23 19:05, Linden via Emc-users wrote:
Hello All,
In the early stages of converting a 13 x 24 inch manual Chinese
lathe to run with Linux CNC.
I have 2 questions regarding replacing the Z axis lead screw with a 3205
ball screw:
What I am thinking is mounting the fixed end in a pillow block at the
head stock end of the lathe and the floating end in a second pillow
block at the tail stock end of the bed. The question I have is there any
reason I shouldn't drive the ball screw from the floating end? My logic
for driving at the floating (tali stock) end is 1 I have more room for
belt reduction at this end and 2 with the fixed end of the ball screw
at the head stock end is that the ball screw will be in tension when it
is pulling the carriage toward the head stock during cutting and less
likely to flex or bend.
The second question I have is what would be a realistic cutting speed
range for the ball screw in RPM? The servo motor I am using has a top
speed of 3000rpm and I am trying to figure out reduction ratio that is
realistic.
Thats a pretty husky screw. I driving from the headstock end with the
thrust bearing at the headstock end of a 25mm by 1450mm screw. Accuracy
wise as long as the thrust bearing mount is dead solid it should just work.
Another thing because ball screws and swarf don't mix is seal up the
screw areas, so I filled the top of the cross feed and sealed the bottom
of the carriage below the much smaller screw driving the cross feed. I
also bought a pair of bellows that will extend to around 1400mm and made
4 shouldered barbs that plug into the bellows on each side of the ball
nut, and at the bearings, leaving 2 of the the ball nut bolts out but
drilling those two empty holes on thru to allow the air trapped inside
the bellows to blow through the bolt holes when it is moving rapidly,
rapidly in this case might be and end to end of over 1.3 meters at 120
or more carriage speed.
You pay good money for the screws, protect them.
Thanks in advance for any help or suggestions.
And I hope everybody has a better 2024. And had a merry Christmas.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
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